Charge-transporting thin films are used in organic electroluminescent (EL) devices. Methods of forming such charge-transporting thin films are broadly divided into dry processes such as vapor deposition and wet processes such as spin coating. These processes are selectively used as appropriate according to the surface area of the thin film to be formed and the solubility in organic solvents of the substance to be rendered into a thin film.
In general, between the anode and the light-emitting layer of an organic EL device, there are two layers—one called the hole-injecting layer and another called the hole-transporting layer—arranged in this order from the anode side. By providing two such layers, efficient charge transport is possible, enabling an organic EL device having high brightness characteristics to be obtained (see, for example, Non-Patent Document 1). Yet, on the other hand, organic EL device production processes also have the drawback that independent steps are normally required to form these respective layers.
Recently, in the field of electronic devices, in order to efficiently manufacture devices at a high yield, there has existed a desire for process simplification and greater simplicity in the device structure. In particular, by replacing a functional multilayer film obtained by stacking a plurality of films in the device with a single-layer film, not only can the manufacturing process be simplified, it is also possible to directly simplify the device structure. Hence, in connection with various electronic devices, there exists a desire for materials capable of producing functional single-layer films that can be substituted for existing functional multilayer films. In the field of organic EL devices as well, there is a growing desire for materials that can replace a functional multilayer film typically composed of a hole-injecting layer and a hole-transporting layer with a single-layer film.